Sources close to the confirmation process say Hagel has prepared for the hearing in private sessions that were designed to mimic the grilling he will face from both sides of the aisle.

“Hagel is very comfortable with his record and his experience,” said a source close to the confirmation process. “One of the things that plays to his strength here is once people are able to hear him lay out his worldview in the open, I think it will really re-frame the way that the conversation has gone.

“He’s eager to have that opportunity,” the source said.

Republicans are just as hungry for the clash, and have honed their rhetoric for what could be one of the most contentious confirmation hearings in recent memory.

“He’s the same person that suggested that the United States might be able to live with a nuclear Iran,” Cornyn said. “In other words, Hagel has no credibility on the biggest security issue facing the Obama administration in its second term.”

Conservative groups have a lot riding on the outcome of the battle, having spent considerable sums on television ads and websites that portray Hagel as unfit to lead the military.

Hagel has been building support on Capitol Hill in a series of private, one-on-one conversations with senators. Those meetings seemed to have won over Democrats who were initially skeptical of his nomination.

“What you’ve seen from key senators, key leadership folks, and most recently with Cochran, is a steady stream of folks saying, ‘I met with him, I talked with him, and I can be openly and vocally supportive,” said a source close to Hagel’s confirmation.

Opponents have tried to turn the tide against Hagel’s confirmation by highlighting controversial statements he made in the past about Israel, Iran and gay people.

Hagel will have to answer to past statements that have been repeated frequently by opponents, such as his comments that the “Jewish lobby” intimidates Washington and his remark that a diplomatic nominee was “aggressively gay.”

Anticipating the onslaught, officials working to aide Hagel’s confirmation have circulated a “myths and facts” document that addresses his record as Republican senator. He also submitted a 112-page response to questions from the committee ahead of Thursday’s hearing.

In that document, Hagel addressed allegations that he would be soft on America’s enemies, saying his is “committed to considering all options to counter Iran and its aggression.”

Lawmakers have also indicated they will press Hagel over his assertion in 2011 that the Pentagon budget was “bloated,” and over potential reductions to the U.S. nuclear arsenal.